I went to 25ACP in my Omega due to the crud ring. Yes, it got rid of the crud ring, but there are more benefits.

I did not see enough of an accuracy advantage to know for certain it is there. I perceive fewer flyers, but I will not tell you that with certainty.

I do find the ACPs much cleaner and with less blowback.

Personally one of the biggest advantages is handling. I'd always drop the 209s into the action when I tried to get them out. With cold hands, it was very difficult to manipulate them. The 209s are longer and much easier to handle -- I never had a problem getting them in and out.

I've heard from people using 209s that burn out their breechplugs after several hundred rounds of shooting -- the flashhole enlarges and accuracy goes. I can't say this for sure, but I have many hundreds (a thousand?) rounds through my Omega and there has been no loss in accuracy. It is possible that with the weaker small rifle primer it does not burn out the plug.

Omega/Encore plugs are easy to convert yourself using the right drill bit and a lathe or drill press with vise.